Mental shield
A mental shield is a supernatural power that blocks any and all kinds of powers acting on the mind, not necessarily malevolent ones. Two people show it in the books: Bella Swan, who displays it in its most advanced and developed form, and her father Charlie, who shows it in its most undeveloped and rudimentary form. Description As a human, Bella considered this power a 'glitch' in her head; Edward had teased her that he could only read FM minds, and that she was on AM. Her shield seems to be based on her "private mind", a place where no one can harm her. It also made her very desirable to Aro, who likes to collect vampires with special abilities for the Volturi guard. Three months after her becoming a vampire, Eleazar correctly describes it as a shield. With the help of Eleazar, Kate and Zafrina, Bella learns to gain some control over it, eventually coming to include a number of other individuals in her shield at the same time. This comes useful in Breaking Dawn when she includes her family and friends under it, protecting them from the powers of Jane, Alec, or any of the Volturi guard. She also learns to remove it to allow mental powers to work on her, as to allow Edward to read her mind. While her main shield is pushed out to protect others, a secondary shield also surrounds her personally. She can manipulate it in any way she pleases, either by wrapping around her targets like plastic or turning it into a giant dome. It also works as a one-way glass, allowing the powers of the shielded vampires to work undisturbed. Bella mentions that she can sense those she is shielding, since they somehow become part of her. In the case of shape-shifters, a cascading effect has been observed: shielding an Alpha allows protection of the entire pack. In battle, Bella needs to be protected from physical attacks in order to keep her shield around her allies. Control Bella initially had a very hard time pushing it up, describing it as an elastic recoil. This obstacle mainly comes from her subconscious desire to protect her mind above all else. Once she learns to let go of that desire, she gains complete control over it, able to shape it in any way she pleases (even make it wrap around her targets like living plastic), though it takes concentration to make it work properly, even make it follow the movements of those she protects. This comes handy when she removes Kate from her shield while still protecting Garrett. At the end of Breaking Dawn, Bella removes her shield to allow Edward to read her mind. She describes this as much more difficult than pushing it out, as it struggles to protect her and it takes all of her concentration to make it disappear altogether. Limitations Though this shield is powerful, it has many limitations. For instance, it cannot work against a physical attack, allowing for an intruder to attack directly. Renesmee Cullen is the only individual capable to penetrate it, as she can place thoughts and images into her mother's mind. Alice Cullen manages to get around it, because her ability allows her to sense the outcomes of decisions already made, which would probably relate more to the flow of time than to the mind of individuals. Bella also can't block Jasper Hale's ability to control emotions; Marcus's ability to read relationships as seen when he reads the love between her and Edward; Siobhan's ability to affect reality; Benjamin's control of natural elements because it's a purely physical power; James's tracking sense; and Fred's ability to physically repulse others. Similar abilities *Renata, Aro's personal bodyguard in the Volturi, has the power to repel physical attacks, much like how Bella's shield repels mental powers. However, it is limited by making the pursuer want to go in another direction. *Afton has the power to shield himself from attackers by making them think he is invisible. His power is more limited in that he can only shield himself and can be seen through by sharp focusing. Since his power only makes others think he is invisible, this power most likely works on a mental basis. *Fred has the power to induce those around him with a sense of revulsion to drive them away. Those power serves a great purpose in protecting him from pursuers.